| A | B |
|---|
| weather | condition of Earth's atmosphere at a particular time and place |
| atmosphere | mixture of gases that surround the Earth |
| ozone | form of oxygen that has three oxygen atoms in each molecule instead of the usual two; a toxic form of oxygen |
| water vapor | invisible gaseous form of water |
| air pollution | change to the atmosphere that has harmful effects |
| emissions | solid particles and gases released into the air from a smokestack or a motor vehicle |
| photochemical smog | a brownish haze that is a mixture of ozone and other chemicals, formed when nitrogen oxides, hydrocarbons, and other pollutants react with one another in the presence of sunlight |
| temperature inversion | condition in which a layer of warm air traps polluted air close to Earth's surface |
| acid rain | rain that is more acidic than normal, caused by the release of molecules of sulfur dioxide and nitrogen oxide into the air. |
| ozone layer | layer of the atmosphere that contains a higher concentration of ozone than the rest of the atmosphere |
| chlorofluorocarbons | chlorine compounds formerly used in air conditioners, refrigerators, and spray cans |
| greenhouse effect | process by which heat is trapped in the atmosphere by water vapor, carbon dioxide, methan, and other gases that form a "blanket" around Earth |
| global warming | a gradual increase in the temperature of Earth's atmosphere |
| density | amount of mass in a given space; mass per unit volume |
| pressure | amount of force pushing on a surface or area |
| air pressure | force that is the result of of the weight of a column of air pushing down on an area |
| barometer | an instrument used to measure changes in air pressure |
| mercury barometer | instrument that measures changes in air pressure consisting of a glass tube part filled with mercury, with its open end resting in a dish of mercury |
| aneroid barometer | an instrument that measures changes in air pressure without using a liquid |
| altitude | elevation above sea level |
| troposphere | lowest layer of Earth's atmosphere, where weather occurs |
| stratosphere | second lowest layer of Earth's atmosphere; the ozone layer is located in the upper part of this |
| mesosphere | middle layer of Earth's atmosphere; layer in which most meteroids burn up |
| thermosphere | the outermost layer of Earth's atmosphere |
| ionosphere | lower part of the thermosphere where electrically charged particles called ions are found |
| aurora borealis | colorful, glowing display in the sky caused when particles from the sun strike oxygen and nitrogen atoms in the ionosphere; the Northern Lights |
| exosphere | the outer layer of the thermosphere, extending outward into space |
